// needs to take care of such type expressions.
	if op, _ := x.(*syntax.Operation); op != nil && (op.Op == syntax.Tilde || op.Op == syntax.Or) {
		t := check.typ(&syntax.InterfaceType{MethodList: []*syntax.Field{{Type: x}}})
		// mark t as implicit interface if all went well
		if t, _ := t.(*Interface); t != nil {
			t.implicit = true
		}
		return t
	}
	return check.typ(x)
}